docs: def open_resource(name):
      """Open a resource from the zoneinfo subdir for reading.
  
      Uses the pkg_resources module if available and no standard file
      found at the calculated location.
      """
      name_parts = name.lstrip('/').split('/')
      for part in name_parts:
          if part == os.path.pardir or os.path.sep in part:
              raise ValueError('Bad path segment: %r' % part)
      filename = os.path.join(os.path.dirname(__file__),
                              'zoneinfo', *name_parts)
      if not os.path.exists(filename):
          # http://bugs.launchpad.net/bugs/383171 - we avoid using this
          # unless absolutely necessary to help when a broken version of
          # pkg_resources is installed.
          try:
              from pkg_resources import resource_stream
          except ImportError:
              resource_stream = None
  
          if resource_stream is not None:
              return resource_stream(__name__, 'zoneinfo/' + name)
      return open(filename, 'rb')